1. Field of the Invention
The present invention relates to novel curable and cured organosilicon compositions, and to processes for preparing these compositions.
2. Description of Background and Other Information
LEIBFRIED '779, U.S. Pat. No. 4,900,779, LEIBFRIED '731, U.S. Pat. No. 4,902,731, LEIBFRIED '134, U.S. Pat. No. 5,077,134, and BARD et al '360, U.S. Pat. No. 5,008,360, describe crosslinked organosilicon polymers and crosslinkable organosilicon prepolymers comprising alternating polycyclic hydrocarbon residues and cyclic polysiloxanes or siloxysilane residues linked through carbon to silicon bonds; these patents are incorporated herein in their entireties, by reference thereto. COWAN, U.S. Pat. No. 4,877,820, also incorporated herein in its entirety, by reference thereto, discloses crosslinkable and crosslinked linear poly(organohydrosiloxane) prepolymers and polymers having at least 30% of their hydrosilation reactive .tbd.SiH groups reacted with hydrocarbon residues derived from polycyclic polyenes.
More specifically, LEIBFRIED '134 discloses certain cyclic siloxanes as comprising mixtures containing up to about 20% (in purer forms as low as 2%) low molecular weight linear siloxanes, such as heptamethyltrisiloxane, octamethyltetrasiloxane, hexamethyl disiloxane, etc. LEIBFRIED '134 also discloses crosslinked polymers comprising alternating polycyclic polyene residues and polysiloxane/siloxysilane residues derived from (i) cyclic polysiloxanes or tetrahedral siloxysilanes, and (ii) linear, short chain .tbd.SiH terminated polysiloxanes. The preferred linear, short chain .tbd.SiH terminated polysiloxanes are disclosed as having the general formula: ##STR2## wherein n is 0 to 1000 and R is alkyl or aryl, preferably methyl or phenyl. LEIBFRIED '134 further discloses a preferred method in which polycyclic polyenes and cyclic polysiloxanes or tetrahedral siloxysilanes are used to prepare prepolymers, followed by mixing linear, short chain .tbd.SiH terminated polysiloxanes with the prepolymer, and curing the mixture in the presence of a hydrosilation catalyst. In this process, the linear, short chain .tbd.SiH terminated polysiloxanes are used in an amount of 10 to 50% by weight of the polysiloxanes and siloxysilanes added to the preformed olefin reaction product. The linear polysiloxanes are disclosed as imparting flexibility to the cured polymers, and can be used to produce elastomers.
COWAN '820 discloses crosslinked or crosslinkable linear poly(organohydrosiloxane) wherein the crosslinking units are derived from polycyclic polyenes. These polymers are prepared by reacting or partially reacting the poly(organohydrosiloxanes) with polycyclic polyenes in the presence of a hydrosilation catalyst. The resulting polymers are characterized in that the organohydrosiloxane is a linear poly(organohydrosiloxanes) having at least 30% of its .tbd.SiH groups reacted with hydrocarbon residues derived from polycyclic polyenes. COWAN '820 discloses preferred linear poly(organohydrosiloxanes) of the general formula: ##STR3## wherein R is a substituted or unsubstituted, saturated alkyl radical or a substituted or unsubstituted phenyl radical, and about 1% to about 50%, preferably 5% to about 50%, of the R's are hydrogen, and m is an integer from about 5 to 1000, preferably 5 to 100, and the maximum value of m is desirably 40.
The polymerization of commercially available linear methylhydrosiloxanes (LMHS) with hydrosilation reactive olefins, such as polycyclic polyenes, to produce silicon carbon reactive polymers (SC reactive polymers), has been hampered in the past due to the low glass transition temperatures (T.sub.g &lt;100.degree. C.) and low modulus, of the materials produced by reacting LMHS with dienes, such as dicyclopentadiene (DCPD).